[P-EM15] Study of coupling processes in solar-terrestrial system

[PEM15-12] Basic structures of the dayside polar ionosphere at higher latitude than the auroral zone during periods of the solar minimum and maximum

*Hitoshi Fujiwara¹, Satonori Nozawa², Yasunobu Ogawa³ (1.Education and Research Center for Sustainable Development/Faculty of Science and Technology, Seikei University, 2.Institute for Space-Earth Environmental Research, Nagoya University, 3.National Institute of Polar Research)

Keywords:polar ionosphere, EISCAT radar, polar cap region, solar cycle

Long-term observations lasting more than 10 years are extremely important for understanding the nonlinear processes and natures of the solar-terrestrial system. We have been conducting dayside ionospheric observations using the EISCAT radar system since 2011. In particular, we have focused our scientific attention on ionospheric fluctuations/disturbances in the polar cap region. Our observations have revealed that the ionosphere in the polar cap region shows some fluctuations not only during periods of disturbances such as geomagnetic storms, but also during times of geomagnetically quiet. Since there have been few observations of the ionosphere and thermosphere in the dayside polar cap region, there are many things that we do not fully understand. Understanding the structure and fluctuations of the ionosphere during geomagnetically quiet periods during both the solar minimum and maximum will lead to an understanding of the fundamental state of the polar cap ionosphere. During the solar minimum period, there are valuable data sets of the ionospheric observations with the EISCAT radar system during 2007-2008 (IPY period) and 2019-2020. On the other hand, solar activity is currently reaching its maximum period, and our EISCAT radar observations have continued during this period. We will compare the basic structures of the polar cap ionosphere (or the ionosphere at the higher latitude than the auroral zone) between the solar minimum and maximum periods. In addition, wave-like fluctuations in the ionosphere, which are usually seen in the ion temperature data, will be compared during the periods.